Video storage type communication device for selectively providing coded frames for selectable reproduction speed and mode according to type of a terminal device

ABSTRACT

A device which is capable of storing moving picture data received from each terminal and providing each terminal with video information to be reproducible by rapidly forwarding or reversing at any desired speed independent of usable terminals. A video storage type communication device 30 with a receiving portion 35 and a transmitting portion 38 transmits and receives video data over a communication network 10 to and from each terminal l-n. A coded video data received from terminals l-n is stored as it is in a first storage portion 32 and, at the same time, the data converted into specially reproducible video information is stored in the second storage portion 33. At the time of reproducing, the reproduction control portion 35 controls the reproduction selector switch 36 to obtain the video data from the first storage portion 32 or the second storage portion 33, changing the reproduction mode from ordinary to the rapid forwarding/reversing and vice versa. The specially reproducible video generating portion 34 successively restores coded video data received through the receiving portion 31, encodes again the restored data by intraframe, interframe or still-picture coding method to generate video information to be reproducible in special mode such as reproduction by rapid forwarding or reversing.

This application is a continuation, of application Ser. No. 08/508,077filed on Jul. 27, 1995, now abandoned, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a video storage type communicationsystem and more particularly to a video storage type communicationdevice which is capable of successively decoding received coded videodata by video decoding means, encoding the decoded video frame/field(hereinafter simply referred to as frame) only in intraframe mode bycoding means and stored in a center storage device, thereby realizingthe possibility of generating pictures specially reproducible, forexample, with rapid feeding.

Recently, with the spread and progress of digital transmission lines andthe advance of image processing technology based upon the development ofhigh speed digital signal processing methods and related LSI technology,there has been an increasing demand for development of effective methodof using video information services using high-speed digitalcommunication networks, e.g., ISDN (Integrated Services DigitalNetworks). Video telecommunication services and a video conferencingservices are well known as currently available video communicationservices. The most newly emerging services are video informationdatabase services which allow each user by using his audiovisualterminal set (referred to as a terminal) to access a database storage(recording device) of a host center and to obtain desired videoinformation therefrom. One of these systems is a storage typecommunication device for use in a host center, which is intended tocontrol storing video information in a center storage and reproducingthe video information at each terminal from the host center.

A conventional storage type communication system for providing a videostorage-and-delivery service has a video storage type communicationdevice, a video storage portion, a communication control portion, areceiving portion, a transmitting portion and etc., and a video datacoded by any one of the terminals is transmitted over the communicationnetwork to the receiving portion. The receiving portion divides areceived coded video-data into frames and transmits the frames to thevideo storage portion, and the video storage portion stores the receivedcoded video-data (frames) therein according to an instruction given bythe communication control portion. The video storage type communicationdevice is intended to be connected with an audiovisual terminal(hereinafter abbreviated to AV terminal) which conforms therecommendation ITU-T (International Telecommunications Union) and meetsthe recommendation H.261 on a video information coding system.

In the video storage and communication services, it is desired toprepare functions of video reproduction with rapid forward or rapidreverse feeding. However, video data coded according to therecommendation H.261 is usually coded by interframe coding method andtherefore consists of differential information. If a first frame data isinterframely coded, each receiving terminal can not restore the frameinto an image (i.e., a screenful) but have only confused screen imagefor a while. Therefore, data of the first frame is not interframely butintraframely coded and stored. The recommendation H.261 proposes toperiodically refresh a system component for preventing erroraccumulation due to interframe coding and to periodically conduct anintraframe coding of moving picture data. By using this opportunity, asequence of the data frames are stored with an intraframely coded frame(data) placed at the head thereof. This makes it possible to reproducevideo with a rapid feed by thinning the data units (frames) whenreproducing the video data stored.

A video storage type communication device which realizes rapid-feedreproduction of images by using periodical refreshment is disclosed inJapanese Laid-Open Patent Publication No. 5-91497. The disclosed deviceis featured by that whenever a rapid feed control is carried-out, it canstart from intraframely coded data, i.e., data of the heading(intraframely coded) frame of interframely coded frames, assuring thesynchronized processing visual data and audio data.

The above-mentioned structure of stored data, however, is featured bycoexistence of the data necessary for usual reproduction and the datanecessary for rapid-feed reproduction. Therefore, it is required tocontrol a storage and data for correctly distinguishing theabove-mentioned two kinds of data from each other when reproducing them.Furthermore, the rapid-feed reproduction requires such reproductioncontrol that may select and read only data necessary for rapid-feedreproduction. All these facts may require much complicated data controlwhen storing and reproducing the data. In addition, as mentioned above,periodical refreshment depends upon terminals which have differentperiod of intraframe coding, depriving the storage and communicationdevice of the possibility of controlling a speed of rapid-feedreproduction.

Furthermore, the recommendation H.261 provides that video data coding isconducted on each of blocks into which one frame of video data isdivided for encoding, whereas refreshment is conducted on a macroblockconsisting of a plurality of the blocks which may not correspond to oneframe. Therefore, some terminals may not guarantee that the whole of aframe is intraframely coded.

It is possible to force a terminal to intraframely encode a whole videoframe and receive the intraframely coded frame therefrom by sending asignal requesting "fast update" from the video storage typecommunication device. However, since timing is not defined, thereceiving side has to discriminate whether the received frames areintraframely coded or interframely coded by checking all frames one byone macroblock. Data control may be much complicated.

SUMMARY OF THE PRESENT INVENTION

It is an object of the present invention to provide a video storage typecommunication device which is capable of storing video (moving picture)data and reproducing the stored data by a usual method and by a specialmethod of rapidly forwarding or reversing at a speed selectivelyadjustable independent of a usable terminal by using its storing andreproducing means which is capable of easily controlling the usuallyreproducible video data and specially reproducible video data.

It is another object of the present invention to provide a video storagetype communication device which is capable of generating, separatelyfrom the ordinary reproducible video data, video data to be speciallyreproducible for example by rapid forwarding and rapid reversing byusing a reproducible video generating portion and a second storageportion for storing the specially reproducible video data generated bythe specially reproducible video generating portion, and which is alsocapable of independently operating the ordinarily reproducible videodata storage and the specially reproducible video data storage, therebypermitting the relatively free addition and change of their functions.

It is another object of the present invention to provide a video storagetype communication device which is capable of easily changing over itsoperating mode from the ordinary reproducing mode to the speciallyreproducing mode and vice versa in such a manner that its reproductioncontrol portion switches over two readable storage portions to selectrequired one, thereby making it easier to control the data to bereproduced.

It is another object of the present invention to provide a video storagetype communication device which is capable of rapidly reproducing videoinformation in a forward or reverse direction starting from any framewithout requiring specially adapted terminals by such a manner that aspecially reproducible video generating portion prepares a speciallyreproducible video data by intraframely encoding restored video (movingpicture) data.

It is another object of the present invention to provide a video storagetype communication device which is capable of preparing videoinformation by interframely encoding restored video data by itsspecially reproducible video generating portion, which can be reproducedby rapid feeding at a terminal having a low ability of decoding movingpictures.

It is another object of the present invention to provide a video storagetype communication device which is capable of preparing videoinformation consisting of still-picture frames by still-framely encodingrestored video data by its specially reproducible video generatingportion; the still-framely coded video information, in comparison withthe intraframely coded video information, has an increased codingefficiency assuring the possibility of storing a larger amount of datahaving a higher quality; these still frames can be easily reproducibleby rapidly forwarding or reversing like moving pictures even at aterminal having no ability of decoding coded moving pictures.

It is another object of the present invention to provide a video storagetype communication device which has a storage control portion forselecting video information from a specially reproducible videogenerating portion and video information from a receiving portion andstoring the selected video information in a storage portion, therebymaking it possible to insert and store specially reproducible videoinformation in any position among video information received from aterminal.

It is another object of the present invention to provide a video storagetype communication device which has a communication control portionbeing capable of instructing a storage control portion to selectspecially reproducible coded video information from a speciallyreproducible video generating portion at a specified interval, therebymaking it possible to store the specially reproducible video informationat any desired interval, or making it easier to control a skippinginterval when reproducing video information at rapidly forwarding orreversing.

It is another object of the present invention to provide a video storagetype communication device which has a reproduction control portion forcontrolling a call for video information from a video storage portionaccording to an instruction to be given by a communication controlportion, making it possible to switching over reproduction modes(ordinary, rapid forwarding and rapid reversing) and to adjust a speedof rapid forwarding and reversing.

It is another object of the present invention to provide a video storagetype communication device which has a specially reproducible videogenerating portion comprising a decoding portion for decoding codedvideo data received through a receiving portion and a still-picturecoding portion for coding the video information restored by the decodingportion by a still-picture coding method, making it possible to simplyreproduce moving picture in forwarding and reversing directions even ata terminal which has no ability of decoding a H.261 class movingpicture.

It is another object of the present invention to provide a video storagetype communication device provided with an intraframe coding portion forintraframely encoding the restored video (moving picture) data, whichcan store in separate frames only the intraframely coded video data in avideo storage portion, thereby making it possible to process editing,adding, deleting and exchanging data therein.

It is another object of the present invention to provide a video storagetype communication device is provided with a video-reproduction controlportion for controlling a process of calling for video data from thevideo storage portion, which can realize selectively switching avideo-reproduction mode from a normal reproduction to rapid forwardingor rapid reversing and vice versa and changing a speed of rapidforwarding and rapid reversing.

It is another object of the present invention to provide a video storagetype communication device which is capable of decoding the coded videodata by a second video-restoring and newly encoding the restored videodata by an intraframe coding portion before transmitting forreproduction, thereby transmittable data frames have reduced amount ofdata than that of intraframely coded frames, assuring much effective useof a communication network.

It is another object of the present invention to provide a video storagetype communication device which is capable of decoding the coded videodata by a second video-restoring and newly encoding the restored videodata by a still-picture coding portion, thereby the obtained stillframes can be easily reproduced even at a terminal having no ability ofdecoding a coded moving picture according to the recommendation H. 261.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a construction view of a video communication system applied tothe present invention.

FIG. 2 is a construction view of a conventional video storage typecommunication device.

FIG. 3 shows an example of refreshing process in a conventional storagetype communication device.

FIG. 4 is a construction view for explaining a video storage typecommunication device embodying the present invention.

FIG. 5 is a construction view of a specially reproducible videogenerating portion shown in FIG. 3.

FIG. 6 shows a correlation between received data and stored data.

FIG. 7 is a construction view of another example of speciallyreproducible video generating portion according to the presentinvention.

FIG. 8 is a construction view of a further example of speciallyreproducible video generating portion according to the presentinvention.

FIG. 9 is a construction view for explaining a video storage typecommunication device embodying the present invention.

FIG. 10 is a construction view of an embodiment of a speciallyreproducible video generating portion shown in FIG. 9.

FIG. 11 is a construction view of another embodiment of speciallyreproducible video generating portion shown in FIG. 9.

FIG. 12 is a construction view of an exemplified storage control portionshown in FIG. 9.

FIG. 13 is a flow chart of video data for explaining the operation ofthe storage type communication device.

FIG. 14 is illustrative of stored video frames in a storage typecommunication device according to the present invention.

FIG. 15 is a construction view of a video storage type communicationdevice embodying the present invention.

FIG. 16 is a view showing a correlation between received data and storeddata.

FIG. 17 is a construction view of another example of avideo-reproduction control portion according to the present invention.

FIG. 18 is a construction view of a further example of avideo-reproduction control portion according to the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 is illustrative of a system of conducting a video-informationdatabase service, which includes terminals l-n, a digital transmissionnetwork 10 and a video storage type communication device 20. FIG. 2 is adetailed illustration of the video storage type communication deviceshown in FIG. 1. As shown in FIG. 2, the video storage typecommunication device 20 comprises a receiving portion 21, a refreshedpicture detecting portion 22, a transferring portion 23, a communicationcontrol portion 24, a video storage portion 25, a reproduction controlportion 26, transmitting portion 27 and so on. The receiving portion 21and the transmitting portion 27 are connected to the digitaltransmission network 10 for communication with the terminals l-n.

The storage type communication device 20 is intended to be connectedwith the terminals l-n which conform to the video coding method H.261recommended by International Telecommunications Union (ITU).

In the video storage type communication services, it is desired toprepare functions of video reproduction with rapid forwarding or rapidreversing. However, video data coded according to the recommendationH.261 is usually coded by interframe differential coding method and,therefore, consists of differential information. If the first frame datais coded by interframe coding method, each receiving terminal can notrestore the frame into a picture (i.e., a screenful) but have onlyconfused screen image for a while. Therefore, data of the first frame isnot interframely but intraframely coded and stored. The recommendationH.261 proposes to periodically refresh the video data for preventingerror accumulation due to interframe coding and to periodically conductan intraframe coding of moving picture data. By using this opportunity,the frames of video data are stored in such a way that a frame ofintraframely coded video data is placed at the head of a video datasequence. This makes it possible to reproduce video information byrapidly forwarding or reversing by thinning frames at a specifiedinterval.

The above-mentioned periodical refreshment, however, depends uponterminals which may have different period of intraframe coding,depriving the storage type communication device of the possibility ofcontrolling a speed of rapidly feeding reproduction.

FIG. 3 shows an example of refreshing process in a conventional storagetype communication device. At the moment when periodical refreshment iscarried-out at a terminal, intraframely coded video data frames A0, B0,C0 and so on are inserted at indefinite intervals. Coded video data istransferred to a terminal in the order of frames A0, B0, C0 and so onwhen they are reproduced by rapidly forwarding and in the order offrames C0, B0, A0 when they are reproduced by rapidly reversing. Namely,frames are reproduced rapidly but at irregular feeding speed at theterminal. This is undesirable from the view point of the servicequality. In view of the foregoing circumstances, the present inventionwas made to provide a video storage type communication device which hasvideo storing means being capable of storing coded video data receivedfrom terminals and reproducing the video data by an ordinary method aswell as by a special method, e.g., by rapidly forwarding and reversingat a speed selectively adjustable independent of terminals used.

FIG. 4 is a construction view for explaining a video storage typecommunication device embodying the present invention.

In FIG. 4, l-n are terminals, 10 is a communication network and 30 is avideo storage type communication device according to the presentinvention. The video storage type communication device 30 trough itsreceiving portion 31 and transmitting portion 38 is connected with thecommunication network 10, over which it communicates video data to andfrom a plurality of the terminals l-n. The first storage portion 32 hasstoring media for storing therein coded video data received from thereceiving portion 31 according to an instruction to be given by thecommunication control portion 37. Data to be stored in the first storageportion 32 is interframely coded data A shown in FIG. 6 consistingmainly of coded interframe differential information which has adecreased data amount but is unsuitable for reproduction by rapidforwarding or reversing.

The coded video data from the receiving portion 31 is also transferredto the specially reproducible video generating portion 34 wherein it isconverted into specially reproducible video information which is thentransferred to the second storage portion 33. Like the first storageportion 32, the second storage portion 33 has storing media for storingtherein coded video data generated by the specially reproducible videogenerating portion 34 according to an instruction to be given by thecommunication control portion 37.

The video data stored in the first storage portion 32 and the video datastored in the second storage portion 33 are read out by the reproductioncontrol portion 35. The video data is read from the first storageportion 32 for ordinary reproduction while the video data is read fromthe second storage portion 33 for special reproduction. At the sametime, the reproduction control portion 35 operates the reproductionselector switch 36 so that it selects the data required to betransferred to the transmitting portion 38. The transmitting portion 38receives the data from the first storage portion 32 or the secondstorage portion 33 and transmits the data to the terminals l-n over thecommunication network 10.

FIG. 5 is illustrative of a specially reproducible video generatingportion shown in FIG. 4. In FIG. 5, there is shown a speciallyreproducible video generating portion 34 including a video restoringportion 34a, an intraframe coding portion 34b and a speciallyreproducible video generation control portion 34c. The video restoringportion 34a restores video data by successively decoding coded videodata received through the receiving portion 31. The intraframe codingportion 34b intraframely encodes the video data restored by the videorestoring portion 34a. The control portion 34c for generation ofspecially reproducible video data performs control operations forgeneration of specially reproducible video data, e.g., selection offrames to be intraframely encoded. By applying another coding portionhaving another encoding means, e.g., still-picture coding means inaddition to the intraframe coding portion 34b, it is possible to adaptedto various kinds of coding formats.

With the thus constructed specially reproducible video generatingportion, video data to be stored in the second video storage portion 33is such that the received coded video data is thinned off frames at aspecified interval and encoded, in form of, e.g., intraframely codeddata B shown in FIG. 6. In comparison with the interframely coded dataA, the intraframely coded data B has a larger amount of data per framebut frames are independent and, therefore, can be reproduced with nodisturbance despite the order of reading them. When these video framesare read and transmitted in the order of storing, they can be rapidlyreproduced at terminals. On the other hand, when these video frames areread and transmitted in the reverse order, they can be rapidlyreproduced in the reverse direction.

As described above, a heading video data is desired to be intraframelycoded frame. Accordingly, even in ordinary reproduction, only a frame tobe first reproducible is read from the second storage portion andreproduced and, then, the second and succeeding frames are obtained fromthe first storage portion and reproduced.

If there is video information that is previously known to be reproducedonly in ordinary mode or desired not to be rapidly reproduced, allcomponent frames except the heading one are not subjected to decoding,intraframe coding and storing into the second storage portion. This maysave unnecessary use of memory capacity of the second storage portion,thereby assuring effective use of its storing media.

Since video information stored in the second storage portion 33 consistsof intraframely coded data which is separated per frame, it permitsrelatively easy processing for edition, addition, deletion and exchangeof the data as may be required.

FIG. 7 is a construction view of another example of a speciallyreproducible video generating portion. The specially reproducible videogenerating portion 34 includes a video restoring portion 34a, aninterframe coding portion 34d and a specially reproducible videogeneration control portion 34c. The video restoring portion 34a restoresvideo data by successively decoding coded video data received throughthe receiving portion 31 of FIG. 4. The interframe coding portion 34dinterframely encodes the video data restored by the video restoringportion 34a. The control portion 34c for generation of speciallyreproducible video data performs control operations for generation ofspecially reproducible video data, e.g., selection of frames to beinterframely encoded.

With the thus constructed specially reproducible video generatingportion, the interframely coded video data may be adapted only for rapidreproduction, but video information to be reproduced is obtained bythinning frames of the received coded video data and, therefore, may bereproduced at a terminal having a low ability of decoding video (movingpicture) data. As compared with the above-mentioned first example, theinterframe coded data is smaller size per frame in storage, resulting insaving storing media of the storage portion.

FIG. 8 is a construction view of a further example of a speciallyreproducible video generating portion. The specially reproducible videogenerating portion 34 includes a video restoring portion 34a, astill-picture coding portion 34e and a specially reproducible videogeneration control portion 34c. The video restoring portion 34a restoresvideo data by successively decoding coded video data received throughthe receiving portion 31 of FIG. 4. The still-picture coding portion 34eencodes the video data restored by the video restoring portion 34a intoa still picture (frame). The control portion 34c for generation ofspecially reproducible video data performs control operations concerninggeneration of specially reproducible video data, e.g., selection offrames to be encoded by still-picture coding method.

An ordinary algorithm of coding a still-picture is defined by therecommendation T.81 of ITU.

With the thus constructed specially reproducible video generatingportion, an obtainable coded still-picture frame in comparison with theintraframely or interframely coded video data has a larger amount ofdata per frame but is reproducible as simply moving pictures at aterminal which can not decode coded data of moving pictures or at adisplay directly connected with the video storage and communicationdevice. The still coded frames can be reproduced in forwarding andreversing directions because they do not correlate with each other.

The application of a coding portion having still-picture coding meanstogether with the aforementioned intraframe and interframe codingportions makes it possible to comply with various kinds of codedformats.

FIG. 9 is a construction view for explaining another embodiment of videostorage type communication device according to the present invention.

The video storage type communication device 40 through its receivingportion 41 and transmitting portion 47 is connected with thecommunication network 10, over which it communicates video data to andfrom a plurality of terminals l-n.

The coded video data received by the receiving portion 41 is transferredto the specially reproducible video generating portion 42 and thestorage control portion 43 under the control of a communication controlportion 45. The coded video information is conventional video dataencoded by a hybrid coding method that is a combination of motioncompensative interframe prediction coding and intraframe orthogonaltransformation coding.

As shown in FIG. 10, the specially reproducible video generating portion42 consists of a decoding portion (H.261) 42a and an intraframe codingportion (H.261) 42b and successively decodes coded video data receivedthrough the receiving portion 41 to restore video information. At thistime, like a usual H.261 type decoder, the decoding portion 42a performsprocessing operations such as motion compensative interframe predictiondecoding and reverse DCT (Discrete Cosine Transform). The video datarestored by the decoding portion 42a according to the recommendation H.261 is then encoded only in the intraframe mode defined in therecommendation H. 261 by the intraframe coding portion 42b from whichthe coded video information is outputted.

Accordingly, the specially reproducible video generating portion (H.261) 42 has no need for performing the interframe prediction coding,being relieved of motion compensative prediction processing which isconsidered as main processing load for an ordinary H.261 type coder. Itis also relieved of necessity for having frame memory for that purpose.Namely, the portion 42 has to perform very simple processing operations,just like a still-picture decoder, and, therefore, has a simplehardware.

FIG. 11 illustrates another example of a specially reproducible videogenerating portion 42 which comprises a decoding portion (H. 261) 42aand a still-picture coding portion 42c. The decoding portion (H.261) 42asuccessively decodes coded video data received through the receivingportion 41 (FIG. 4) to restore video information. At this time, like ausual H.261 type decoder, the decoding portion 42a performs processingoperations for motion compensative interframe prediction decoding andreverse DCT (Discrete Cosine Transform). The still-picture codingportion 42c encodes the restored video information by applying astill-picture coding algorithm defined in the recommendation T.81 ofITU.

With the thus constructed specially reproducible video generatingportion, obtainable still-frames of coded video data in comparison withthe intraframely or interframely coded video data have a larger amountof data per frame but are reproducible as simple moving pictures at aterminal which can not decode coded data of normal moving pictures or adisplay directly connected with the video storage type communicationdevice. This can be realized by controlling the reproduction controlportion 46 so as to send only coded still-frames to the terminal or thedisplay when reproducing the video data.

The application of the coding portion having still picture coding meanstogether with the aforementioned intraframe coding portion makes itpossible to comply with various kinds of coded formats.

The communication control portion 45 provides the storage controlportion 43 with control information necessary for starting and finishingthe storage operation and distinguishing which kind of video informationis stored--received frame video information or coded video information.

Referring to FIG. 12, the storage control portion 43 consists of a videoinformation selecting control portion 43a, a selector switch 43b and atransferring portion 43c, According to control information from thecommunication control portion 45 for starting, ending and storingreceived frame video information or coded video information, the storagecontrol portion 43 selects the received frame video information from thereceiving portion 41 or the coded video information from the speciallyreproducible video generating portion 42 by operating the selectorswitch 43b, and transfers the selected video information together withadditional information indicating, e.g., intraframe or interframe modeof the storable data to the video storage portion 44 for storing theinformation therein.

FIG. 13 is a flow chart for explaining the operation of the videostorage type communication device embodying the present invention. Codedvideo data from a terminal is received by the receiving portion 41(Step 1) and then transferred to the specially reproducible videogenerating portion 42 and the storage control portion 43.

In the specially reproducible video generating portion 42, the codedvideo data is decoded by the H.261 type decoding portion 42a (Step 2)and stored in a frame memory thereof. The video frames (screenfuls) areread from the frame memory of the H.261 type decoding portion 42a andare intraframely coded by the H.261 type intraframe coding portion 42b(Step 3). The intraframely coded video data frames outputted from theH.261 type intraframe coding portion 42b are transferred to the storagecontrol portion 44.

The storage control portion 43 determines which coded videodata--intraframely coded video data (output of the speciallyreproducible video generating portion 42) or interframely coded videodata (output of the receiving portion 41) is transferred to the videostorage portion 44 according to an instruction given by thecommunication control portion 45 (Step 4). When the instruction from thecommunication control portion 45 indicates storing intraframely codedvideo data, the coded video data is complemented with an informationindicating the data being intraframely coded data and, then, transferredto the video storage portion through the transferring portion 43c. Withthe instruction indicating storing interframely coded video data, thecoded video data with information indicating the data being interframelycoded data is transferred to the video storage portion through thetransferring portion 43c. (Step 5)

The communication control portion 45 directs the storage control portion43 not to store video data when said data is not required; to storevideo data coded in interframe mode when storing interframely codeddata; and to store video data coded in intraframe mode when storingintraframely coded data. The communication control portion may requeststoring video data intraframe mode or interframe mode at desiredintervals.

FIG. 14 shows an example of storing coded video data from a terminalinto a storage by using the video storage type communication deviceaccording to the present invention. For easier understanding, such acase is described that coded data from the terminal can be transmittedat a constant frame rate (the number of frames to be transmitted persecond). In case of FIG. 14, video data coded in the intraframe mode isinserted at a specified interval. Frames A0, B0, C0 and D0 are ofintraframely coded video data. Frames A1-A2, B1-B2, C1-C2 and D1 are ofinterframely coded video data. In the shown case, the frames ofintraframely coded video data are inserted among the frames ofinterframely coded video data at an interval of 1:3.

In reproduction of the stored video data, the communication controlportion 45 directs the video storage portion 44 to read-out the storedcoded video data therefrom. The communication control portion 45 alsogives the reproduction control portion 46 a reproduction controlinformation necessary for ordinary reproduction or reproduction byrapidly forwarding or by rapidly reversing (e.g., reproducible storedcoded video data, direction relative to time axis, the number of framesper unit time for skipping reproduction). According to the informationgiven by the communication control portion 45, the reproduction controlportion 46 reads the required coded video data from the storage portion44 and transferred the data to the transmitting portion 47 which in turntransmits the received coded video data to the terminal.

Referring to FIG. 14, the stored coded video data is transmitted to aterminal whereat it is reproduced in an ordinary mode, rapidlyforwarding mode or rapidly reversing mode.

In the ordinary reproduction, it is possible to transfer frames ofintraframely coded video data and frames of video data coded by themotion compensative interframe prediction coding method. Therefore,frames A0, A1, A2, B0, B1, B2, C0, C1, C2. D0, D1 can be transmitted inthe described order to the terminal.

In reproduction by rapidly forwarding, the frames of video data coded bythe motion compensative interframe prediction coding method can not betransmitted to the terminal because the latter can not correctly performpredicted compensation. Therefore, only frames of intraframely codedvideo data are transmitted in the order of A0, B0, C0, D0 or A0, C0 andso on to the terminal.

In reproduction by rapidly reversing, like the reproduction by rapidlyforwarding, only frames of intraframely coded video data are transmittedbut in the reversed order of D0, C0, B0, A0 or D0, B0 and so on to theterminal.

FIG. 15 is a construction view for explaining a video storage typecommunication device embodying the present invention.

A video storage type communication device 50 is connected at itsreceiving portion 51 and transmitting portion 57 with a communicationnetwork 10 over which it transmits video data to and from a plurality ofthe terminals l-n.

The video restoring portion 52 restores video (moving picture) data bysuccessively decoding coded video data received through the receivingportion 51. The intraframe coding portion 53 intraframely encodes thevideo data restored by the video restoring portion 52. A video storageportion 54 has data storing media and stores the video data transferredfrom the intraframe coding portion 53 according to an instruction givenby a communication control portion 55.

The video data stored in the video storage portion 54 is read-outtherefrom by the video-reproduction control portion 56. According to aninstruction of the communication control portion 55, thevideo-reproduction control portion 56 successively reads coded videoframes in the order of their storing in the storage portion 54 when theyare to be ordinarily reproduced, whereas it reads the frames at acertain interval in the forward or reverse order when they are to bereproduced by rapidly forwarding or reversing. The transmitting portion57 receives the video data transferred from the video-reproductioncontrol portion 56 and transmits the received video data over thecommunication network 10 to terminals l-n.

In the thus constructed video-storage type communication device, videodata stored in the video storage portion 54 is intraframely coded framesB shown in FIG. 16, which, in comparison with received coded video data,i.e., interframely coded frames A, have a larger amount of data perframe and can be read out in any order and be surely reproduced at anyterminal because the frames have no correlation between their contents(data). When these frames reads-out in the order of storing at a certaininterval and transmitted, they are reproduced in rapid forwarding modeat the terminals. When the frames read-out in the reversed order at acertain interval, they are reproduced in rapid reverse mode at theterminals. The stored frames are independent from each other and may beprocessed separately, making it easier to edit, add, delete and exchangecomponents as the need be.

FIG. 17 is a construction view of another embodiment of a video storagetype communication device according to the present invention. In FIG.17, numeral 56 designates a video-reproduction control portion which iscomposed of a reproduction control portion 56a, a reproduction selectorswitch 56b, a second video-restoring portion 56c and an interframecoding portion 56d.

The second video restoring portion 56c, like the video restoring portion52 of FIG. 15, restores video (moving picture) by successively decodingcoded video data from a video storage portion 51. The interframe codingportion 56d interframely encodes the video data restored by the secondvideo-restoring portion 56c. The reproduction control portion 56acontrols a calling interval of the video frames from the video storageportion 54 and effects the reproduction selector switch 56b to selectthe necessity or non-necessity of newly encoding the read-out videodata. The reproduction control portion 56a also executes controloperations on the above-mentioned portions for reproduction of the videodata.

With the thus constructed video-reproduction control portion, all framesexcept the first frame can be decoded and newly encoded by the secondvideo-restoring portion 56c and the interframe coding portion 56drespectively before transmitting for reproduction in ordinary or rapidforwarding or rapid reversing mode. By so doing, the frames (except thefirst one) to be transmitted become to have a reduced amount per frameas compared with the embodiment of FIG. 15 whereby the intraframelycoded frames B (FIG. 16) obtained from the video storage portion 54 aretransmitted. Namely, the shown embodiment can much effectively use thecommunication network.

FIG. 18 is a construction view of another embodiment of a video storagetype communication device according to the present invention. In FIG.18, numeral 56 designates a video-reproduction control portion which iscomposed of a reproduction control portion 56a, a reproduction modeselector switch 56b, a second video-restoring portion 56c and astill-picture coding portion 56e.

The second video restoring portion 56c, like the video restoring portion52 of FIG. 15, restores video (moving picture) by successively decodingcoded video data from a video storage portion 54. The still-picturecoding portion 56e receives the video data restored by the secondvideo-restoring portion 56c and encodes the received video data frame byframe to obtain still-picture frames. An ordinary algorithm of coding astill-picture is defined by the recommendation T.81 of ITU(International Telecommunication Union). The reproduction controlportion 56a controls a calling interval of the video frames from thevideo storage portion 54 and effects the reproduction selector switch56b to select the necessity or non-necessity of newly encoding theread-out video data. The reproduction control portion 56a also performscontrol operations on the above-mentioned portions for reproduction ofthe video data.

With the thus constructed video-reproduction control portion 56,obtainable coded still-picture frames in comparison with theintraframely or interframely coded video frames have a larger amount ofdata per frame but are reproducible as a simplified moving picture at aterminal having no ability of decoding coded moving pictures or at avideo display set directly connected with the video storage typecommunication device. The still-picture coded frames can be reproducedin both (forward and reverse) directions because they do not correlatewith each other.

The application of a coding portion having still-picture coding meanstogether with the aforementioned interframe coding portions makes itpossible to comply with various kinds of coded formats.

We claim:
 1. A video storage type communication device, comprising:atransmitting portion for transmitting video data to and a receivingportion for receiving interframely and intraframely coded video datafrom a communication network; a first video storage portion for storingthe received interframely coded data; a communication control portionfor controlling said transmitting and receiving portions; a speciallyreproducible video generating portion for generating, from the codedvideo data received from the communication network, video information tobe specially reproduced in a specially reproduction mode, said speciallyreproducible video generating portion obtaining a specially reproduciblevideo by intraframely coding and interframely coding video data restoredfrom said coded video data which is received from said receivingportion; and a second storage portion for storing the video informationgenerated by said specially reproducible video generating portion,wherein the received interframely coded video data and the generatedvideo information are stored in parallel with each other into said firstand second storage portions, respectively.